#include <fstream>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int v[500001];
int d[500001];
int main()
{
    int n,k,i,inc=0,sf=0;
    long long s=0;
    cin>>n>>k;
    for(i=1;i<=n;i++)
        cin>>v[i];
    for(i=1;i<=n;i++){
        while(inc<=sf && v[d[sf]]>=v[i])
            sf--;
        d[++sf]=i;
        if(i>=k){
            if(d[inc]<=i-k)
                inc++;
            s+=v[d[inc]];
        }
    }
    cout<<s;

    return 0;
}